Lamps and light sources for general illumination may take many forms. With respect to lighting used in retail settings (as well as for residential, hospitality, hospital, education, museums, and commercial lighting, etc.), lamps or light sources with high color rendering index (CRI) have historically been desired. Incandescent and halogen lamps have historically been the typical types of light sources used to provide the desired characteristics for such settings. In addition to, or instead of, high color rendering, some light sources may provide high color preference, whereby some or most colors have enhanced appearance compared with a reference illuminant (e.g., enhanced-color products of GE under the REVEAL® brand). The lamps and light sources may also provide directional illumination satisfying the desired beam distribution properties of the application. These historical light sources usually have fast warm-up and response time, high light intensity output, and have good color rendering or color preference characteristics, but may suffer from poor efficacy and relatively short lamp life. More recently developed high intensity discharge (HID) lamps, and especially ceramic metal halide (CMH) lamps, may offer much higher efficiency than the historical lamp types, with high CRI, high color preference, and higher beam intensities, but could suffer from insufficient lamp lifetime, poor color control over life and from lamp-to-lamp, and higher cost.
Although these existing technologies provide generally acceptable performance, further enhancement in performance, and/or color quality, and/or reduction in manufacturing cost, and/or increased wall plug energy efficiency, and/or increased lamp life and reliability would be desirable.
In recent years, light sources based upon solid state light (SSL) emitters (e.g., light emitting diodes or LEDs; laser diodes or LDs; and organic light emitting diodes or OLEDs) have come to the forefront by virtue of their very high efficiency in converting electricity into light, long life, as compared to incandescent and halogen lamps, variety of available colors enabling spectral tailoring, small size and high brightness, and rapidly declining cost. This invention is primarily concerned with new capabilities to illuminate white and colored objects by virtue of the spectral tailoring opportunities enabled by SSL light sources.
Many known LED chips (sometimes referred to as dies) may contain at least one semiconductor layer comprising a semiconductor material, such as, but not limited to: a gallium nitride, a zinc oxide, a silicon carbide, or combinations thereof. For example, many known LED chips may comprise a nitride compound semiconductor of In, Ga, Al and N, such as one which is represented by the formula IniGajAlkN (where 0<i; 0<j; 0<k and i+j+k=1).
Many known LED-based light sources have been configured to produce light that appears to be substantially white, for use in general illumination applications and many specialty applications such as retail settings. Many known LED-based light sources possess tailored spectral power distribution of light to achieve excellent color-rendering properties, especially with respect to Color Rendering Index (CRI) and rendering of certain red colored objects (e.g., R9).
There is a general desire to continuously improve white LED lamps for use in illuminating retail merchandise items such as clothing, and retail merchandise settings, especially with respect to white and brightly colored garments or retail merchandise settings having a mixture of white and colored objects. Of course, such light sources may also be the preferred illuminant in applications other than retail merchandise, such as e.g., residential, hospitality, education, museum, hospital, grocery, dining, commercial, and other color-sensitive applications.